Tellurium

Crystalline tellurium appears as a silvery white material that, when pure, gives off a metallic lustre. It is also easily pulverised and quite brittle. It exhibits different conductivity results depending on its crystal alignment and is a p-type semiconductor. Its conductivity increases slightly when exposed to light and it can be doped with other elements such as tin, gold, copper, and silver etc. The chemical family, chalcogen, to which tellurium belongs, includes; polonium, selenium, sulphur and oxygen.

Tellurium Discovered in Romania in 1782

Tellurium was first found to exist in gold ores by the Trannsylvanian chief inspector of mines, Franz Joseph Moller von Reichenstein, in 1782. It was first isolated by M. Klaproth, in 1798, who also gave it its name, which is Latin for Earth (Tellus, the goddess of Earth). The ores examined by von Reichenstein were mined at Zlatna, close to where Sibiu in Romania is located.

Tellurium is a Rare Element in the Earths Crust

Tellurium is sometimes found in its native form as an elemental crystal and is far more common in the universe than it is on Earth. It is a very rare element in the crust of the Earth, much like platinum is. This is because it formed a volatile hydride that caused it to be lost to space as a gas when the Earth was being formed. Gold is normally discovered in an uncombined form but when found in nature as a chemical compound it is usually combined with tellurium.

Tellurium Caused Second Gold Rush on the Streets of Kalgoorlie in 1896

During the 1893 gold rush in Kalgoorlie miners often discarded the pyritic material in their search for gold in its pure state. This discarded waste was used as roadfill and in the construction of walk ways. The discarded pyritic material was later discovered to be calaverite, which is a telluride of gold that had gone un-noticed. This discovery created a follow-up gold rush in 1896 in which streets were dug up.

The Many Uses of Tellurium

Tellurium is used in many ways such as in the colouring of ceramics and glass. It is also one of the main ingredients used in the making of blasting caps. Its primary use in the past has been as an alloying agent when it was found that when small amounts of tellurium were added to stainless steel and copper it made them easier to mill and machine. It is also added to lead to increase its resistance to sulphuric acid and to give it more strength. Tellurium is also used in the following fields:

• As cadmium telluride in solar panels
• In solid state x-ray detectors
• As a tellurium suboxide in the making of rewritable optical discs, rewritable compact disks such as DVD-RW and in the making of Rewritable Blu-ray disks
• As tellerium dioxide in the making of acousto-optic modulators for confocal microscropy
• In the making of new phase change memory chips
• Lead telluride and bismuth telluride is used as working elements in thermoelectric devices
• Lead telluride is used in far-unfrared detectors
• The vulcanising of rubber to improve its heat resistance

Most tellurium used today is sourced from the anode sludges made when electrolyticly refining blister copper. It is also found as a component of dust when blast furnacing in the refining of lead. Commercial tellurium is usually sold as a 200-mesh powder. It is also marketed in lumps, sticks, ingots and as slabs.